1. Field of the Invention
An adjustable chair for human dental or medical treatment, beauty parlors, barber shops, or the like.
2. Description of the Prior Art
As is generally known, almost all of dental treatments today are with the patient being treated in lying position. That means that the lying position is easier for treatment than is sitting up position, and is also comfortable for the patient as well; yet, a complete satisfaction was still unobtainable with the conventional chair.
That is, in the conventional chair, the headrest was being set up so as to make its expansion and contraction possible to the vertical direction of the headrest with a supporting plate, and the lower part of headrest as its supporting point, was being set up so as to make its angle of elevation of movement possible. And, when working on the upper or the lower row of dental arch while the patient in lying position, the headrest had to be moved all the way to the front or to the back so to facilitate the treatment; in such case, however, that in the aforementioned conventional method, since there occurred a difference between the supporting point of the movement of angle of elevation of the headrest and the supporting point of the movement of the same direction of the patient's head, the cervical vertebrae made a large unnatural bent, and in addition, such position, though depending upon the nature of treatment, had to be maintained somewhere from several minutes to 20 or even more minutes. Therefore, it might have been easier for the treatment, but certainly was undesirable as far as the comfort of the patient was concerned.
The prior art includes motor driven configurations, for adjusting the components of a dentist's chair relative to one another. Typical of the prior art is U.S. Pat. No. 3,027,194 which discloses a headrest with a curved shank that has several dimples formed therein. The dimples cooperate with spring-loaded balls, to define the locked position for the headrest relative to a vehicle seat. U.S. Pat. No. 3,542,428 discloses an adjustable headrest which has a curved linear member, that enables the same to be adjusted relative to the back of an automotive seat. Other prior art of interest includes U.S. Pat. Nos. 694,683; 910,357; 2,481,133; 2,987,116; 3,578,379 and 3,836,197.